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By R. Hardy

LaModel is a boundary-element program capable of calculating the displacements and stresses in thin bedded deposits such as coal, salt, or potash. Throughout its history, it has continually been upgraded in order to expand analysis detail and stay current with the latest advances in computer technology. The most recent enhancements include: an increased grid size capability, a significant increase in the speed of the automatic grid generation using an AutoCAD visual interface, implementation of subsidence-based horizontal strain calculations for multiple-seam situations, and pillar safety factor calculations. To demonstrate these new features, a multiple-seam case study of a longwall panel undermining an active set of main entries is presented.

Jan 1, 2006

By Michael Feroz

Severe drought in the Colorado River Basin over the past 10 years has caused water levels to drop in Lake Mead by more than 113 feet. The current lake level is at elevation 1,112 feet mean sea level (msl). Lake Mead is the primary source of water supply for greater Las Vegas. Water for Las Vegas from Lake Mead is accessed through two existing submerged intake shaft and tunnel systems. If the water levels continue to drop in the lake, the Intake No. 1 will become inoperable below water level elevation of 1,050 feet msl. To sustain the current levels of water delivery to all member agen-cies in the southern Nevada region, the Southern Nevada Water Authority (SNWA) has decided to construct a third intake at a deeper depth in the lake to ensure better quality water and enhanced reliability.

By S. Holtermann

Through the process of Riverbank Filtration (RBF), the Louisville Water Company plans to obtain a higher quality source of water for their B.E. Payne Water Treatment Plant (WTP) by means of four collector wells located in the alluvial aquifer along the bank of the Ohio River. The collector wells are connected to a 2,850 L/s (65 mgd) pumping station by a 2,362 m (7,750 ft) long, 3 m (10 ft) finished diameter tunnel located in limestone and shale bedrock, which is approximately 45 m (150 ft) below the surface. High tunnel boring machine (TBM) production rates were achieved in this moderately weak bedrock; most of the tunnel only required support in the crown. An unanticipated water-bearing fault and unanticipated ground behavior proved challenging and required quick thinking to minimize impacts to construction. Tunneling conditions are discussed in detail, together with the methods used for overcoming the groundwater and ground behavior challenges. The tunnel is expected to be completed in April 2009.

By S. M. Jasinski

Peat is a natural organic material of botanical origin. Peatlands are situated predominately in shallow wetland areas of the Northern Hemisphere. Commercial deposits are formed from the gradual decomposition of plant matter under anaerobic conditions for about 5,000-years. In 2004, peat was harvested in 16 states. Florida, Michigan and Minnesota accounted for more than 80 percent of the U.S. production. Reed-sedge was the dominant variety of peat harvested in the United States, comprising almost 80 percent of the output. This was followed by humus, hypnum moss and sphagnum moss.

Jan 1, 2005

By P. Conrad

Experience has shown that, since the passage of the Surface Mining Control and Reclamation Act, over-compaction of spoil during the reclamation process has severely limited tree growth on reclaimed land. Researchers at the University of Kentucky have conducted a ten-year investigation at a surface mine in eastern Kentucky that monitored the changes in selected spoil physical characteristics for various reclamation and compaction alleviation methods. More specifically, research plots were developed for reforestation that employed three different levels of compaction and two different methods of ripping for overly compacted spoil. Each year measurements were made in the field of dry bulk density, using a nuclear density gage, and maximum penetration depth, using a recording cone penetrometer. In addition to good correlation between tree growth and selected spoil characteristics, the data demonstrated a gradual convergence of the measured spoil characteristic data over the study period.

Jan 1, 2008

By William R. Yernberg

The combined 79th Annual Minnesota Section of SME Meeting and 67th Annual University of Minnesota Mining Symposium was held April 11 and 12, 2006, in Duluth, MN. About 300 mining professionals attended, including engineers, executives, mining managers and suppliers, from throughout the United States and Canada. This year’s theme was “Success in the New World of Mining.” The SME Minnesota Section meeting included a keynote session, a special projects update, a general managers update and technical paper presentations. The University of Minnesota Mining Symposium program featured a panel discussion on Minnesota’s relationship with China. The combined meeting included a trade-show consisting of 64 booth spaces. Tradeshow demand exceeded expectations, and an additional 10 booth spaces were added in the registration lobby. Also included were an SME short course on pump basics and social events.

Jan 1, 2006

By R. Mensah-Biney

The NC State University Minerals Research Laboratory (MRL) and Waste Reduction Partners (WRP) of the Land of Sky Regional Council joined efforts in 2000 to initiate a technically sound and practical program for the management of high-volume coal combustion by-products (CCBs) in North Carolina. The accumulation of CCBs from coal burning boilers throughout the state of North Carolina posed a substantial storage problem, and the area was overripe for an effective management program, which would be environmentally sustainable. In particular, the public utility generators had filled storage ponds on their properties, and the storage overload had grown to critical proportions. Much the same situation existed for paper mill biosolids, which were stored on site in landfill cells along with daily output of CCBs from the mill boilers. A conversion process via the patented pyro-process12 (US Patent No. 5,342,442) to produce synthetic light weight aggregates (LWA) from CCBs and paper mill sludge was conceived to process large quantities of both these waste materials. MRL and WRP initiated and formed a consortium that brought together academia, private industry and state agencies to evaluate the production of LWA by the pyro-process. The industry partners included representatives from the power companies, industrial ash generators, expediters for coal ash products, as well as concrete block manufacturers. It was important to welcome interested parties from not only the western North Carolina area and other parts of the state but also from neighboring states including Tennessee, South Carolina and Georgia. Membership of this consortium evolved during the intervening years to include the following participants and supporters: Progress Energy Carolinas; Duke Energy; Santee Cooper; Full Circle Solutions; Land-of-Sky Regional Council; NC Department of Pollution Prevention and Environmental Assistance; Ecusta Business Development Center; Blue Ridge Paper Products; Jackson Paper and Manufacturing Company; Miller Perlite; Appalachian Products; General Shale Brick; Metromont Materials; Small Business Technology Development Center of the University of North Carolina system and North Carolina State University The initial development program conducted at the Minerals Research Laboratory (MRL) was to formulate an acceptable LWA product, which fulfilled user specifications for light weight concrete block and structural concrete application. Support work and program coordination efforts were furnished by retired technical volunteers in WRP. The work advanced steadily, using proven technologies well established in the mineral industry, to generate a very satisfactory LWA. The consortium then concluded that a more comprehensive CCB conversion program would have more appeal for full scale manufacture and commercialization, if a variety of products from CCB separation were generated. This product assortment would include bottom ash, low carbon fly ash, recovered carbon of high purity, as well as the synthetic LWA. The bottom ash would serve the concrete block market, the fly ash was in demand for ready-mix concrete, and the high carbon product could be pelletized and used as a fuel for reburn or by the steel industry, and the LWA was a sought-after component for light weight concrete applications. After scouting all these potential markets and finding them to be viable, the consortium then inaugurated an integrated pilot plant program for the CCB separation and conversion. The plan was organized in three (3) parts: (1) Phase I ? bench scale evaluation studies (2) Phase II continuous pilot plant evaluation and (3) Phase III ? conceptual commercial plant design including marketing efforts and attraction of business entrepreneurs to build a full scale manufacturing plant. Phase II would serve to validate the process in a continuous mode and produce substantial quantities of products for preliminary marketing efforts and for demonstration-of-use purposes. The consortium agreed to the name, CAROLINA ASH PRODUCTS, (CAP), for the integrated pilot plant program. The products generated might be designated with the CAP label as: bottom ash would be named CAP Granules, low carbon fly ash would become CAP Ash, recovered high carbon product would be CAP Carbon, and LWA would have the name CAP Stone. Phase II of the program processed 20 tons (18 t) of ponded ash from Progress Energy storage at a rate of 600 lb (271 kg) of raw ash per hour with favorable results. PRELIMINARY STUDIES Prior to committing laboratory research and development effort as well as support and coordination activities to this program, it was necessary to determine (1) the level of need for a freshly launched CCB reutilization program in this state and (2) what degree of versatility was necessary for such a process. State agency records and a survey of recent boiler operations indicated that in the state of North Carolina at least 77 facilities manage CCBs from their boiler operations. Despite continuing development efforts in more eastern parts of the state, the use of CCBs for commercial applications has not increased to a level which alleviates the need to store vast quantities in private monofills on the generator?s property. More than 1.25 million tons (1.13 million t) of CCBs are landfilled in NC annually, with 300,000 tons (271,985 t) per year generated in western NC alone. Many different boiler types, which span both very old units and those that are modern and efficient, were to be found. These included stoker-fired units, pulverized coal boilers, slag-tap furnaces, and fluidized bed combustion boilers covering a range of sizes. Any systems designed to separate CCB components from all these sources and convert them to useful secondary products would need broad processing latitude and flexibility. Up to the present there has been a paucity of research done in the western part of the state to find productive alternatives to storage in landfills. With tipping fees in our largest landfill now approaching $40 per ton ($44 per t) and escalating transportation fees (about $200 per truckload up to 40 tons, traveling a distance of 25 miles), the problem has become urgent both economically and ecologically. A well-designed, integrated wet process for CCB separation into value-added products had much potential to be less expensive than landfilling as well as to provide saleable materials with acceptable profit margins. These preliminary investigations also revealed that other major waste streams, in particular paper mill sludge and municipal and animal waste biosolids were important candidates for priority attention. Since these biosolids could furnish the organic component of a synthetic LWA product, they could be consumed as part of the same program. This added interest value to a growing list of partners to support and participate in the program.

Jan 1, 2009

By T. R. Ellis

Australia’s mineral valuation code continues to evolve, while mineral valuation standards are also being written for Canada and Southern Africa. The author is leading a task force for writing the extractive industries addition to the International Valuation Standards. Meanwhile, the International Accounting Standards Board is continuing the development of an extractive industries addition to its International Financial Reporting Standards, with an emphasis on valuation reporting. This paper analyzes the need, content and ownership for a U.S. minerals appraisal standard in the context of both these developing international standards and also existing U.S. regulations and appraisal standards. The author provides many questions for research and debate.

Jan 1, 2003

By R. Mensah-Biney

The kinetics of loading of gold from bromide solution onto an anion exchange resin, PAZ-4, were investigated in a batch stirred reactor. The initial loading rate was described mathematically by a first-order reaction rate equation. The effect of agitation speed, temperature, resin particle size, resin concentration, initial concentration of gold and bromine in solution on the rate was investigated. The model described fairly accurately the loading process in terms of the variables investigated. The rate constant for the initial loading ranged from 0.5 to 1.3 x10-3 sec-1 and the half-time was 9.3 to 56 minutes. The initial rate constant increased with increasing temperature with an activation energy of 15.7 kJ/mole (3.8 kcal/mole). The rate constant was directly proportional to the concentration of the resin in solution. The subsequent reduction reaction was also modeled by the first-order rate equation and the apparent rate constant was estimated to be 3.0 x 10-6 sec-1 with a half-time of about 44 hours.

Jan 1, 1994

By K. S. Gritton

The implementation of advance control systems brings with it the expectation of improvements in process performance and controllability. Specifically, expectations include a shift in the mean value of the gross measure of process performance, and/or a decrease in process variability. When determining statistically-defensible measures of these benefits care must be taken to preclude process parameters from biasing the determination. Specifically, the effects of ore type, shift personnel, water availability, etc., must all be separated from the effect on performance of the advanced control system. Methods are presented for separating the effects of process control from other process parameters. Examples of the required data analyses are also presented.

Jan 1, 2001

By J. Hunter, E. Jackson

This paper describes work done by Placer Dome Technical Services Limited, a subsidiary of Barrick Gold, and Nautilus Minerals Inc. in support of the conceptual design of a subsea mining system. It describes an overall concept design plus specific studies into mechanical excavation at depth. The concept design includes one or more subsea excavators connected to a suction riser, which transports the cut material to a shipboard dewatering and offloading system. A multi-phase investigation was performed into the mechanical excavation of seafloor massive sulphides at depths of around 1600m. Rock samples were recovered and tested for rock properties and cutting behaviour. A small pick drum cutter was procured and tested on a representative concrete slab in a lab and tested again while submerged in a test tank. Finally the cutter was tested on a massive sulphide ore body at 1600m depth. The cutting performance results, e.g. pick forces and specific energies, should provide valuable input to the design of future full scale subsea mining systems.

Jan 1, 2007

By S. Kittel, P. Galleguillos, H. E. Urtubia

The rougher flotation at Escondida consists of 80 cells of 100 m3 each, with injected air. Escondida has developed a system of automatic control of the rougher flotation using video cameras, which have been operating since 1997 for remote monitoring and manual control. Since 1999, an image processing software and a group of rules have allowed implementation of an expert system. To date, the expert system controls the superficial speed of each cell by adjusting the air flow and the froth depth of the flotation bank. Preliminary tests of the expert control on two of the eight rows gave 1.2% higher rougher recovery at a 92% degree of confidence. The proven benefits are already sufficient to move towards a complete plant implementation.

Jan 1, 2001

By P. Todd, K. Dever, P. S. Mills, A. A. Campoli

Resin bolt performance is dependent on the size of the resin annulus, the difference between the hole and bolt radii. The vast majority of the millions of resin roof bolts installed each year in the United States employ an annulus of 0.125 or 0.188 inches. Short encapsulation pull tests with resin annuluses of 0.125 and 0.095 inch resisted an average of 2.25tons per grouted inch, with no significant variation. Resin loses to simulated fractures increased as annulus size decreased, with a minimum loss of35% and a maximum loss of 60% associated with0.188 and 0.095 inch annuluses, respectively.

Jan 1, 2000

Coal that meets customer specifications is often stored in silos before being loaded into cars. It is often found that coal in a particular car does not meet customer specifications due to the mixing of coal inside the silo. Some new contracts require meeting specifications on a per car basis. Silo flow models are used to predict quality in such cases. However, coming up with an accurate silo flow model for each case is very difficult and time consuming. This paper examines the viability of using an online analyzer at the loading end of the silo in conjunction with a feedback circuit, to optimize the quality of the coal being loaded into trains, so that each car meets quality specifications.

Jan 1, 2000

By K. Awuah-Offei

The objective of asphalt mix design is to produce a mix with optimal performance using available aggregate stockpiles. Often, this process does not take into consideration aggregate plant stockpile inventories or the cost of aggregate in the mix. This is due to the lack of tools that enable the lab technician or the engineer to optimize the mix for good performance while reducing the cost of aggregate and managing the stockpile inventory levels. The Bailey method provides useful guidance on aggregate gradation selection for optimal performance. This work presents a linear programming model of the asphalt mix design problem. The algorithm is implemented in MATLAB as an Asphalt Mix Design Optimization (AMIDO) program. The program is successfully validated with real-life data. The results show that AMIDO can be used to successfully produce any mix design with known Bailey method ratios. Also, RAP can be included in a design easily by making use of the Bailey method ratios and AMIDO. This work improves the state-of-the-art in asphalt mix design for dense graded mixes and could potentially be modified for other mixes.

Jan 1, 2009

By RENE GOMEZ, RAUL CASTRO

Estimation tools and models are now available to estimate fragmentation, but some variables have yet to be studied to understand their effect on the fragmentation process. One such variable whose mechanisms have yet to be studied is the residence time, which in block caving directly depends on the distance that fragments travel from their original position in the broken ore to the drawpoint. In this study, granular material fragmentation was characterized during its flow to understand its characteristics and mechanisms. The results show that the breakage of fragment singularities occurred mainly within medium and smaller sizes, increasing fine material during flow. Thus, the main fragmentation mechanism in experiments was identified as abrasion between rock fragments where fine material continuously increases as distance increases in spite of the high rock strength and the piston flow movement used. The results presented here can be applied to incorporate fragmentation during flow of large travel distance of ore such as in block caving.

By M. Arias

"An attractive foreign investment legislation, an anti-mining framework in the jurisdiction where a head office is located, the geographical location of the mineral resources, a country that offers the technology needed by the industry for its operations -- these are some of the many factors that make mining and mineral exploration a global business. It is precisely in the complexity of this new era of globalization and market environment, that sustainability initiatives are challenged. Responsible management of mineral exploration and mining is no longer defined by the use of efficient technology and resource management. Sustainability is not only a report compliance exercise or a green revolution. Sustainability is like any business, a long term profitable proposition. This new approach encompasses four pillars: social, economic, environment, and culture. This new approach connects humans and corporations; it is the way to engage, respect and improve relations with the people with whom we work and our neighbours."

Jan 1, 2011

By Jeffrey A. Pontius

The Cresson gold deposit is in the southcentral portion of the Cripple Creek mining district in central Colorado (Fig. 1). The deposit is hosted by a series of 32 Ma (Kelley, 1995) felsic to mafic, alkaline volcanic rocks that were deposited in a diatremal environment. Mineralization in the Cresson deposit is structurally con-trolled. It occurs as disseminated and vein type. Gold deposition is closely associated with potassium-pyrite metasomatism and quartz-telluride vein development(Pontius, 1992). The Cresson deposit is owned by the Cripple Creek and Victor Gold Mining Co. (CC&V), a joint venture between Pikes Peak Mining (67%) and Golden CycleGold (33%).

Jan 1, 1996

By Janet A. Flinn, David G. Fileccia

Machine guidance and control systems have become more pervasive in the mining industry in recent years but not always from mining-experienced providers. Dozers, motor graders, scrapers, excavators, shovels, draglines, drills and haul trucks are just a few examples of the types of heavy machinery now equipped with global positioning system (GPS)-aided guidance systems. While equipment manufacturers are offering their own software, many only supply solutions for the machines they produce. The proliferation of GPS equipment manufacturers entering the machine guidance and control arena has resulted in a multitude of makes and models of GPS receivers. Some of these companies also produce their own guidance software. But they usually just specialize in a narrow range of heavy machinery. So customers are forced to use multiple systems and face new challenges in implementation, training, reporting and inter-system communication.

Jan 1, 2006

By J. Wickens

This paper discusses how Bald Mountain Mine dramatically reduced mercury production by treating process solutions with a liquid reagent called UNR 811A. The reagent is marketed by Cherokee Chemical Co., Inc. A summary of the bench tests comparing several different reagents is given. The ensuing plant trial is discussed and results are presented. The plant trial treatment costs are discussed. Finally, potential cost savings are discussed.

Jan 1, 2001